The function
clipboard
returns the contents of the system clipboard as a string, or
nil
if the clipboard is empty.
The Windows clipboard is usually set by the user with the Ctrl+C and Ctrl+X gestures. Note that LispWorks uses these gestures when in Windows emulation mode.
On X, various gestures may set the clipboard. The X clipboard can be accessed by running the program
xclipboard
or the Emacs function
x-get-clipboard
.